Latexes have been used for binding polyester fibers for quite some time. Because of the inherent flammability of polyesters, flame retardant compositions have been added to binders in order to make the bound polyester fibers less fire or flame hazardous than they would otherwise be.
It should be understood that when using the words "flame retardant" or words of similar import herein, it is intended to refer to a composition which "enables a material to resist burning when exposed to a relatively low-energy ignition source, such as a cigarette, match, candle, cigarette lighter, or stove burner." "Flame Retardants--government regulations and public emphasis on safety provide the importance for an expanding industry," CHEMICAL & ENGINEERING NEWS, Apr. 24, 1978, PP. 22-36, 23.
Many chemicals have been used to flame retard fibers. Probably one of the most well known of these chemicals is Tris, tris-(2,3-dibromopropyl) phosphate. This chemical was once used as a flame retardant for children's sleepwear but is no longer used for such a purpose after testing revealed that the compound might be carcinogenic in humans.
Since the advent of the Tris crisis, manufacturers have sought to fill in the gap left by the departed Tris. Some members of the industry have sought to produce inherently flame-retardant fibers thereby obviating the need for flame retardant coatings on the fibers. However, fibers other than those which are inherently flame-retardant are still being produced. Thus, a need still exists for flame-retardant chemicals to be used in coating these fibers.
Chemicals other than Tris have been used as flame retardants for fibers and, in particular, polyester fibers. For example, Stauffer has commercialized Fyrol FR-2, Tris (1,3-dichloroisopropyl) phosphate, as a polyester fiber flame retardant. Mobil Chemical has sold Antiblaze 19, a mixture of two cyclic phosphonate esters, as flame-retardant for polyester fibers. Of course, many other flame retardants are commercially available for use with various fibers.
There have been many disclosures in U.S. patents concerning chemicals useful as flame retardants for many different types of materials. U.S Patent No. 2,036,854 discloses a composition useful in flame proofing textile materials which is a mixture of ammonium borate or phosphate with an ammonium halide such as ammonium bromide. That patent further discloses that the added ammonium halide appears to greatly increase the flame extinguishing properties of ammonium borate or phosphate.
U.S. Patent No. 2,452,054 concerns flame-retardant compositions for cellulosic materials. In that patent there are disclosed chemicals which convert nonresinous carbonific material utilized in the cellulosic material into a foam-like, puffed-up layer which is resistant to combustion. The chemicals disclosed include diammonium phosphate and ammonium bromide.
U.S. Pat. No. 3,058,927 relates to self-extinguishing aromatic polymer compositions. In the patent it is disclosed that the combination of ammonium bromide with certain agents act as synergists to enhance the flame-proofing action of ammonium bromide and render the polymers self-extinguishing. It is further disclosed that it is known to employ an ammonium salt such as ammonium phosphate in combination with ammonium bromide to prevent the flamming of inflammable articles such as fabrics, paper, wood or the like.
U.S. Pat. No. 3,061,492 relates to polyester laminates which are flame-retardant. It is disclosed that ammonium bromide may be used as a flame-retardant for unsaturated polyester resin compositions.
U.S. Pat. No. 3,870,590 discloses the utility of adding one or more flame retardants to polyester fibers. It is also disclosed that a synergistic effect is obtained when one or more flame retardants are employed. Further, it is stated that the more important flame retardant synergists contain a halogen such as bromine or chlorine, antimony, phosphorous or nitrogen.
U.S. Pat. No. 4,049,609 relates to unsaturated polyester resin systems which include flame retardants. It is disclosed that bromine and phosphorous compounds may be used as flame retardants.
U.S. Pat. No. 3,840,488 discloses flame-retardant additives for an aqueous latex of a butadiene-styrene polymer useful for textile treatment and carpet backing application. In that patent it is disclosed that the addition of ammonium bromide and urea as a flame-retardant additive to a latex undesirably reduces the viscosity of the latex. It is further disclosed that the undesirable decrease in the viscosity which is observed by the addition of the ammonium bromide and urea into the latex may be prevented by adding another fire-retardant material to the latex such as a halo alkyl phosphoric acid or salt.
The synergistic effect of combining different flame-retardant compositions appears to be dependent on the flame-retardant composition used and on the particular application. For example, a paper entitled "Requirements For The Flame-Retardant Finishing Of Polyester/Cellulosic Blends" by Katherin V. Stevens and Steven B. Sello discloses that a nitrogen/phosphorous synergistic effect has been observed on certain cotton and polyester/cotton blends which have been treated with nitrogen and phosphorous containing compounds. That paper also discloses that a bromine/phosphorous synergism is observed in combinations of brominated aliphatic or aromatic compounds and organophosphorous compounds. However, it was disclosed that only an additive effect was noted with the combination of an inorganic bromine compound such as ammonium bromide with organophosphorus compounds.
The synergistic effect observed by the combination of phosphorous-containing compounds with halogenated compounds is suggested by Table 1-10 in the 1970 edition of THE CHEMISTRY AND USES OF FIRE RETARDANTS BY JOHN W. LYONS. That table notes that while 5% of a phosphorous containing compound or 12-15% of a bromine-containing compound are required to render polyester polymers self-extinguishing, the combination of 2% of a phosphorous-containing compound and 6% of a bromine-containing compound has the same effect.
Some flame-retardant compounds when added to latexes cause the latexes to become unstable. By unstable it is meant that the latex agglomerates and/or has a significant change in viscosity. In some instances, instability may be caused by adding particular types of flame retardant compounds to latexes which are extremely pH sensitive. Generally, such changes, agglomeration and/or rheological property changes, are undesirable because the latexes cannot be used for their intended purpose. For example, there are many latexes which are unstable to the addition of diammonium phosphate.
It would be desirable to take advantage of the synergistic effect of combining flame-retardant compounds and adding those compounds to a latex to produce a latex having enhanced flame retarding properties without substantially affecting the rheological properties of the latex. It would also be desirable to prepare a flame-retardant compound whose pH can be adjusted to allow use of the compound in extremely pH sensitive latexes. In addition, it would also be desirable to produce a non-toxic additive to latex which might be used as a replacement for Tris.